Artificial blood substitutes based on emulsified perfluorochemicals are capable of sustaining animals that have no red cells and less than 2 percent of their normal plasma protein concentration. Since these animals do not rely on hemoglobin, they survive even in a 10 percent carbon monoxide: 90 percent oxygen atmosphere. Ordinary rats die immediately under these circumstances. Various new perfluorochemicals will be tested both for emulsion stability and retention in tissues. The reasons for the differences betwen perfluorochemicals that are not retained and those that are will be sought. Studies will continue on possible biological effects of these compounds including mammalian cell respiration and metabolism. Long term perfusion of living animals and also of isolated organs will be investigated. Attempts will be made to delineate the nutritional and hormonal requirements that obtain under these conditions of perfusion. Bloodless animals will be studied as models for a number of experiments not possible when red cells and plasma proteins are present. BIBLIOGRAPHIC REFERENCES: Geyer, R.P., K. Taylor, R. Eccles, and E. Duffett. Survival of bloodless rats in 10 percent carbon monoxide. Federation Proc. 35: 828 (abs. No. 3438), 1976. Geyer, R.P. Review of perfluorochemical-type blood substitutes. Proceedings of the Xth International Congress for Nutrition: Symposium on Perfluorochemical Artificial Blood, Kyoto 1975, Igakushobo (Medical Publisher), Osaka, Japan, p. 3-19.